During a banquet on Donald Trump’s visit to Riyadh, dozens of Arab officials jockeyed to take selfies with his daughter Ivanka and her husband Jared Kushner as they mingled in a cavernous ballroom. But among the crowd of the Middle East’s wealthiest and most powerful, the glamorous couple appeared bent on getting one man into their photographs: Mohammed bin Salman, a 31-year-old Saudi royal.

The attention the US president’s daughter and senior adviser heaped on Prince Mohammed last month is illustrative of the meteoric rise of young man virtually unheard of outside Saudi royal circles three years ago.

He was once banned from entering Saudi Arabia’s defence ministry at a time when his father headed it because his brash style alienated bureaucrats. But this week he was anointed crown prince in the absolute monarchy in the most radical shake up of the kingdom’s succession process in decades.

The move cements his position as the most powerful man in the world’s top oil exporter, clearing the path for him to forge ahead with his highly ambitious plans to modernise the deeply conservative nation and wean it off its dependency on petrodollars. The only person he now has to answer to is his infirm, octogenarian father, King Salman — the man who charted his path to the top.

“Today, foreign policy, defence matters, and issues of social change are all under Prince Mohammed’s control. And he will probably have this wide-ranging executive power for many decades to come,” says Mohammed Alyahya, a non-resident fellow at the Atlantic Council.

Prince Mohammed has long been considered a favoured son and a paternal bond developed when he grew up in the same house as his father, who had three wives, while other siblings lived with their mothers.

“This was an unusual upbringing in many ways, reflecting the changing times and reflecting a closer, more western fatherly relationship than others,” says Robert Lacey, author of Inside The Kingdom.

After studying law at King Saud University in Riyadh, he dabbled in real estate and the stock market. But his relationship with his father never dimmed and he became an adviser to his father when he was governor of Riyadh province in 2009.

Saudis in the vicinity used to say they could set their watches by the noise of the Salman’s cavalcade as it arrived promptly at the governor’s office at 8am each day. Prince Mohammed has developed the same work ethic and he regularly works through to 3am, observers say.

When his father ascended to the throne after the death of King Abdullah in 2015, Prince Mohammed was promptly appointed defence minister, and three months later deputy crown prince. His promotion to heir apparent this week meant he leapfrogged his elder, more experienced cousin Mohammed bin Nayef.

As dramatic as the reshuffle was, few in Saudi Arabia were surprised as Prince Mohammed had already become the leadership’s dominant figure at home and abroad.

Mr Lacey says it was the young royal’s meticulous eye for detail that persuaded the ailing King Salman, 81, that his son was the “extra limb” he needed to govern.

King Salman took power as Saudi Arabia was reeling from the collapse in oil prices. Unlike previous kings who were more hands-on, he delegated most of the day-to-day business of running the country to his son who was already developing ideas on how to revamp the economy. Prince Mohammed would tell visitors of the need to break up monopolies, reduce the dominant role of the state, allow private enterprise to flourish and create jobs growing youthful population.

And under his stewardship, Riyadh has laid out plans to do the once unthinkable — sell off a stake in Saudi Aramco, the state oil company that has been the bedrock of economy for decades.

Riyadh is also displaying a newfound boldness in flexing its financial muscle on the international stage — the Public Investment Fund, a once dormant sovereign wealth fund, has splashed out billions of dollars on a flurry of deals, including investments with Uber, the car-hailing back, and Japan’s SoftBank.

All are tied to the prince’s “Vision 2030” and a national transformation plan that targets creating 450,000 private sector jobs within three years, trimming the unwieldy public sector and developing more entertainment in a nation where cinemas are banned.

At the prince’s personal office in the basement of his Riyadh palace, policy meetings can last hours with the heir apparent commanding myriad facts and figures to bolster his arguments. Consultants warn each other to bring their A-game to the meetings. The prince interrupted one when he was in the middle of a presentation with words to the effect of: ‘This is not what I asked for. Please leave,’ says an adviser.

Even before entering government, his detractors accused the tall, heavyset royal of wielding regal influence with an impetuous temper. Some are concerned that these impulsive traits remain, questioning his temperament and judgment.

As defence minister, Prince Mohammed gambled by leading Saudi Arabia into Yemen’s war. Many critics consider it a disastrous campaign and critics accuse Riyadh of killing civilians with poorly-targeted bombing and pushing the Arab world’s poorest country to the brink of famine.

His taste for the high life at time when Saudis are grappling with swingeing austerity has been widely questioned in the kingdom, particularly after reports emerged that he had bought a ‎€500m yacht.

Still, many Saudis are devoted to their “prince of youth,” placing their hopes in his pledge to deliver a more open society. But his promises of radical economic reform may yet alienate generations accustomed to a culture of cradle-to-grave benefits.